This invention relates to ablation devices that are used to create lesions in tissue. More particularly, this invention relates to ablation devices that use vacuum or suction force to hold the tissue in a manner that creates linear lesions.
The action of the heart is known to depend on electrical signals within the heart tissue. Occasionally, these electrical signals do not function properly. Ablation of cardiac conduction pathways in the region of tissue where the signals are malfunctioning has been found to eliminate such faulty signals. Ablation is also used therapeutically with other organ tissue, such as the liver, prostate and uterus. Ablation may also be used in treatment of disorders such as tumors, cancers or undesirable growth.
Currently, electrophysiology (EP) ablation devices generally have one or more electrodes at their tips. These devices may be used for both diagnosis and therapy. In one instance, electrodes at the tips of EP ablation devices allow the physician to measure electrical signals along the surface of the heart. This is called mapping. When necessary, in another instance, the physician can also ablate certain tissues using, typically, radio frequency (RF) energy conducted to one or more ablation electrodes.
Sometimes ablation is necessary only at discrete positions along the tissue is the case, for example, when ablating accessory pathways, such as in Wolff-Parkinson-White syndrome or AV nodal reentrant tachycardias. At other times, however, ablation is desired along a line, called linear ablation. This is the case for atrial fibrillation, where the aim is to reduce the total mass of electrically connected atrial tissue below a threshold believed to be critical for sustaining multiple reentry wavelets. Linear lesions are created between electrically non-conductive anatomic landmarks to reduce the contiguous atrial mass.
Linear ablation is currently accomplished in one of several ways. One way is to position the tip portion of the ablation device so that an ablation electrode is located at one end of the target site. Then energy is applied to the electrode to ablate the tissue adjacent to the electrode. The tip portion of the electrode is then slid along the tissue to a new position and then the ablation process is repeated. This is sometimes referred to as the burn-drag-burn technique. This technique is time-consuming (which is not good for the patient) and requires multiple accurate placements of the electrode (which may be difficult for the physician). Furthermore, even if the ablation process creates a continuously linear line along the top surface of the target tissue, it is not assured that the tissue is continuously and completely ablated through further layers of the target tissue (i.e. it is not assured that transmurality is achieved.)
A second way of accomplishing linear ablation is to use an ablation device having a series of spaced-apart band or coil electrodes which, after the electrode portion of the ablation device has been properly positioned, are energized simultaneously or one at a time to create the desired lesion. If the electrodes are close enough together the lesions run together sufficiently to create a continuous linear lesion. While this technique eliminates some of the problems associated with the burn-drag-burn technique, some repositioning of the ablation device may be required to create an adequately long lesion. In addition, it may be difficult to obtain adequate tissue contact pressure for each electrode in a multi-electrode ablation device. Also, the use of multiple electrodes to create the linear lesion tends to make the tip portion more expensive to make, more bulky and may cause the tip portion to be stiffer than with a single electrodes.
Another ablation-related problem results from the delivery of RF energy to muscular tissue, such as the heart. Ablation of such tissue using conventional ablation devices has a tendency to char or burn the blood or tissue with which the electrodes are in contact if the temperatures exceed a certain threshold (for example, greater than 50xc2x0 C.). This increases the difficulty of the ablation process because it is necessary to clean the tip portion after a series of burns. Moreover, overheating the blood in the vicinity of the target site can desiccate the blood and can cause overburning.
It would be desirable to have an ablation device which is easy to position in relation to the target tissue and which stays stable in position in relation to the target tissue.
It would further be desirable to have an ablation device which, when positioned, is capable of easily creating a linear, transmural lesion.
It would further be desirable to have an ablation device that is able to monitor tissue temperature in order to avoid burning the tissue.
One aspect of the present invention provides a suction assisted ablation device. The device includes a support surface, having a first and a second face, a plurality of suction elements disposed adjacent the support surface on the first face, at least one conductive element disposed adjacent the support surface on the first face; and at least one suction conduit operatively connected with the suction elements. The device may also include a maneuvering apparatus, such as a pull wire assembly. The device may also include at least one thermocouple element. The device may include one conductive element on a first support surface and a separate conductive element on a second support surface. The conductive element may be a plurality of needle electrodes. The device may also include at least one fluid opening, which may be located within the conductive element. The conductive element may also be made of a material capable of releasing fluid.
Another aspect of the invention provides a method of ablating tissue. A suction assisted ablation device comprising a support surface, having a first and a second face, a plurality of suction elements disposed adjacent the support surface on the first face, and at least one conductive element disposed adjacent the support surface on the first face is provided. The first face of the device is placed adjacent an area of tissue. Suction is conducted to the suction elements via the suction conduit. The tissue is grasped with the suction and ablated. At least one fluid outlet may be provided adjacent the support surface and fluid may be released via the fluid outlet. The fluid outlet may be located within the conductive element. The device may be placed using a maneuvering apparatus. At least one thermocouple element may be placed in communication with at least one suction element and a thermal environment of the suction element may be measured using the thermocouple element. The tissue may be ablated until the measurement of the thermal environment reaches a given level. A second support surface having a second conductive element disposed adjacent a first face of the second support surface may also be provided. The first face of the second support surface may be placed in line with the first support surface to complete a circuit. The tissue is ablated.
Another aspect of the invention provides a tissue ablation system. The system comprises at least two support surfaces, each support surface having a first and a second face, a plurality of suction elements disposed adjacent the support surface on the first face, at least one conductive element disposed adjacent the support surface on the first face, at least one suction conduit operatively connected with the suction elements, and at least one maneuvering apparatus, such as a pull wire assembly. The support surfaces may be disposed consecutively to each other in a linear manner along the maneuvering apparatus so that a continuous ablation lesion is achieved. The system may also include a fluid delivery system, which may incorporate at least one fluid opening disposed adjacent the support surface, a fluid conduit, a conductive element including fluid openings or a conductive element made of a material that releases fluid.
Another aspect of the invention provides a method of mapping the heart. A suction assisted ablation device comprising a support surface, having a first and a second face, a plurality of suction elements disposed adjacent the support surface on the first face, at least one electrode disposed adjacent the support surface on the first face and at least one suction conduit operatively connected with the suction elements is provided. The first face of the device is placed adjacent an area of tissue. Suction is conducted to the suction elements via the suction conduit. The tissue is grasped with the suction. A signal is sent through a first electrode. The signal is received through a second electrode. The distance is mapped based on the signal from the first electrode to the second electrode.
Another aspect of the invention provides a method of pacing a heart. A suction assisted ablation device comprising a support surface, having a first and a second face, a plurality of suction elements disposed adjacent the support surface on the first face, at least one electrode disposed adjacent the support surface on the first face and at least one suction conduit operatively connected with the suction elements. The first face of the device is placed adjacent an area of tissue. Suction is conducted to the suction elements via the suction conduit. The tissue is grasped with the suction. Electrical impulses are sent through the electrode at regular interval and the heart is paced to beat with the impulses.
Another aspect of the invention provides a method of ablating tissue. A suction assisted ablation device comprising a support surface, having a first and a second face, a plurality of suction elements disposed adjacent the support surface on the first face, at least one needle electrode disposed adjacent the support surface on the first face and at least one suction conduit operatively connected with the suction elements. The first face of the device is placed adjacent an area of tissue. The tissue is penetrated with the needle electrode. Suction is conducted to the suction elements via the suction conduit. The tissue is grasped with the suction; and ablated.
The foregoing, and other, features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims in equivalence thereof.